Abstract

Aspergillus flavus is a typical filamentous fungus that poses risk to both humans and animals, as well as for crops. The secondary metabolite aflatoxin B1 produced by A. flavus is also one of the most carcinogenic and toxic natural pollutants discovered so far. Lysine benzoylation (Kbz), which participates in various life activities in different organisms, is an important post-translational modification of proteins. Cystathionine β-synthase (CBS) is a key enzyme in the maintenance of the homocysteine balance in organisms. However, the basic mechanism of CBS in the life activities of A. flavus is still unclear. By knocking out the cbs gene, it was found that compared to the wild-type and complementary strains, the cbs deficient strains had lower growth diameter, spore yield and seed colonization, while the number of sclerotia was increased, and toxin accumulation was increased by TLC. We then validated these results through RT-PCR. We also found the existence of a benzoyl site K109 on CBS by immunoprecipitation. Mutation at K109 abolishes benzoylation, resulting in reduced CBS enzymatic activity, which We found that the phenotype of point mutations is consistent with that of knockout strains. In addition, we found that benzoyltransferase GcnE catalyzes the benzoylation of CBS protein and affects enzyme activity. These results not only give theoretical support for the research of cystathionine β-synthase and benzoyl modification, but also provides fresh ideas for the prevention and control of pathogenic fungus A. flavus .